Why do you think Windows "jpg"-ify images? It can use png and gif without conversion. But it needs to scale it down to fit the screen if you select "Fit". You are bound to get artifacts with any scale down; if you want perfection, do the rescaling yourself because you can't expect Windows to read your mind or know what you personally think is perfection.
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PeonNov 18 '12 at 4:37

3

The "screenshot" looks perfectly fine to me, could you more clearly describe the problem?
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kreemoweetNov 18 '12 at 5:31

2

@PeterW. Why are we talking of PNGs anyway when the original you linked to is a JPG as well?
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KaranNov 18 '12 at 21:45

6 Answers
6

I had this problem myself, searched endlessly for an answer and found none. Until I found someone who did not have this problem, I asked them to share their wallpaper with me and I tried it, sure enough, their wallpaper did not have any on screen artifacts and the resulting compressed wallpaper, was not a shrunken down jpg. In fact, the file size of the "compressed" jpg was larger than the original.

So I decided to look around into the settings on the jpg, nothing unusual that I could see, the image was 1900x1200 at 72.009dpi and 8bit. I decided to scale down my own personal wallpapers to the 1900x1200 size, changed the dpi and bitrate to match the other jpg. After saving my new image, I right clicked on it and chose set to desktop, the resulting image has no artifacts and is no longer compressed. This works for every wallpaper I have.

If you try this, I think you need to make sure you change the image dimensions to match that of what your screen resolution is exactly. Also making sure the dpi is set to 72.009 and 8bit. Try it out, see if this helps anyone. I will be posting this message on all the forums and blogs I see discussing this.

Resizing the image to the resolution of display produced a perfect result for me. Without knowing my monitor DPI, I exported the JPG as 300 DPI, quality: 100. I manage my images in Lightroom, so I cropped the image to match the aspect ratio of my monitor. Then in LR, exported with: 300 DPI, Resize to fit: <monitor res>, allow enlarge, JPG, quality 100, Sharpen for screen.
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Alastair McCormackApr 30 '13 at 15:53

There was an answer here, I even upvoted it and accepted it as the correct answer, but it seems to have vanished. It went like this:

Open X:\Users\<User>\AppData\Roaming\Microsoft\Windows\Themes\. The TranscodedWallpaper file inside is a JPG image without a file extension, replace it with a 100%-JPG version of the wallpaper you want to use.

Then, open the CachedFiles folder. Inside should be one or more JPG files, each named like this: CachedImage_2560_1440_POS4.jpg (substitute the numbers with your resolution's width and height). Find the one that matches your active resolution, copy its filename, then delete all the files. Copy your wallpaper's JPG version into this folder as well and rename it to whatever you just copied. The actual resolution of the wallpaper does not matter; as far as I could tell, Windows just reuses whatever wallpaper setting was set. ('Fill' for me)

To make your wallpaper just work (and also to stop the OS from undoing what you've done so far) you'll need to revoke the system user's write access. To do that, fiddle with the security settings of the TranscodedWallpaper file and the CachedFiles folder until it looks like this:

I don't know what these options are called in English versions of Windows, but I imagine their positions to be the same. The first combobox says 'Allow', the second one makes it so that the permissions are applied to all files and folders inside that folder recursively.

When you're done, log out, then log back in again. If you did everything right, your wallpaper shouldn't look like garbage anymore.

Don't set the wallpaper in Windows 8 using Windows Photo Viewer. Windows Photo Viewer saves a lower quality jpeg and uses that as the wallpaper. Use the Control Panel\Appearance and Personalization\Personalization or just right click and select "Set as desktop background".

Also, since you're down-scaling an image you might want to edit/resize it using photoshop to the native resolution of your monitor. Windows is known to produce low quality (ie. rough) downscaling of images and produces the occasional artifacts on wallpapers.

NO. I can confirm this behaviour on Windows 7 64 bit. It occurs for all image types (PNG and BMP) included whenever the user right clicks a thumbnail and chooses "Set as background". I doubt many people notice the behavior because they are not using technical or well drawn backgrounds.

The workaround that worked for me was to open the image (any format) in IrfanView and use that program's "set as wallpaper" feature. It's in the menu under "Options."

I removed the part of the rant, which does not add to the answer. As well, the OP is asking about Windows 8; mentioning Windows 7 does not answer the question, and may make this answer un-useful by itself
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Canadian LukeMar 15 '14 at 20:15

Windows 7 - From what I've tried, you need to use Internet Explorer's right-click -> Set as Background option to retain quality.

I've tried a few file types, and the only way I find to retain quality is to use the program to set the wallpaper. Unfortunately for me, I like to use the slideshow option for my wallpaper, and usually drag (copy) my Pictures to the folder on the customize window.

Even if you use any file type and drag to the Internet Explorer folder where your non-compressed photo shows to be, it will render it as a JPEG.

So from what I can see the only way without modding Windows is to have a solo photo as your wallpaper, which you set through Internet Explorer.